EVAL-INAMP-62RZ/82RZ/82RMZ

Transcription

1 Evaluation Boards for the AD620 Series and and the AD8220 Series Instrumentation Amplifiers EVAL-INAMP-62RZ/82RZ/82RMZ FEATURES 3 generic, easy-to-use PC boards Support several related in-amp products Simple gain setting Decoupled supply lines EVAL-INAMP-62RZ board Tests the AD620, AD621, AD622, and AD623 Configurable for dual or single supplies Provision for optional circuitry Shield driver Adjustable offset/reference EVAL-INAMP-82RZ and EVAL-INAMP-82RMZ boards Test the AD8220, AD8221, and AD8228 Two package variations available: SOIC and MSOP Solder jumper SMA/SMB outline APPLICATIONS Quick, easy product characterization Interface to other evaluation tools Breadboard custom application circuits GENERAL DESCRIPTION This data sheet describes three generic evaluation boards used to test several related in-amp products. A general description of each board is provided in this section. Full details on each of the devices are provided in the device data sheets available from Analog Devices, Inc., and should be consulted in conjunction with this data sheet. EVAL-INAMP-62RZ (SOIC or PDIP) The EVAL-INAMP-62RZ is an easy-to-use accessory for evaluating the AD620 series of instrumentation amplifiers. This board test the AD620, AD621, AD622, and AD623 devices. In addition to the basic in-amp connection, circuit options enable the user to adjust the offset voltage, apply an output reference, or provide shield drivers with user-supplied components. The board is shipped with an assortment of surface-mount packages. The board also has an alternative footprint for a through-hole, 8-lead PDIP. Note that the AD621 CMRR performance degrades at gains of 100 shen using this board due to the high performance of the AD621. To get started with this evaluation board, see the Quick Start for the EVAL-INAMP-62RZ section. EVAL-INAMP-82RZ (SOIC) The EVAL-INAMP-82RZ offers users the option of evaluating the AD8221 and AD8228 instrumentation amplifiers individually or with other products in common applications. As with the AD620 to AD623 board, this board is shipped with an assortment of surface-mount packages. The evaluation board is arranged so that users can easily adjust the gain resistor and reference jumper. The board offers an SMA/SMB outline at the output. Users can add their own connector to interface the evaluation board with complementary tools, such as an analog-to-digital converter (ADC) evaluation board, available from Analog Devices. The board permits easy wiring of active filters, line drives, and ADCs, right on the board, thus extending its use as a development tool. To get started with this evaluation board, see the Quick Start for the EVAL-INAMP-82RZ and EVAL-INAMP-82RMZ section of this data sheet. EVAL-INAMP-82RMZ (MSOP) The EVAL-INAMP-82RMZ board is similar to the EVAL- INAMP-82RZ board with one difference: the EVAL-INAMP- 82RMZ board is configured for the MSOP package. This covers the AD8220, AD8221, and AD8228 products. The EVAL- INAMP-82RMZ board is shipped with an assortment of MSOP surface-mount ICs. To get started, see the Quick Start for the EVAL-INAMP-82RZ and EVAL-INAMP-82RMZ section of this data sheet. BASIC OPERATION The AD620 and AD8220 series in-amps convert a differential input signal to a single-ended output signal, with respect to a reference voltage. User-supplied power supplies connect VS, VS, and ground to pins of the IC. The differential signal is applied to the IN and IN pins of the in-amp, while the signal output appears at the pin of the in-amp. Figure 2 shows the component layout and the location of connections for the EVAL-INAMP-62RZ (AD620 Series) PC board. Rev. A Evaluation boards are only intended for device evaluation and not for production purposes. Evaluation boards are supplied as is and without warranties of any kind, express, implied, or statutory including, but not limited to, any implied warranty of merchantability or fitness for a particular purpose. No license is granted by implication or otherwise under any patents or other intellectual property by application or use of evaluation boards. Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Analog Devices reserves the right to change devices or specifications at any time without notice. Trademarks and registered trademarks are the property of their respective owners. Evaluation boards are not authorized to be used in life support devices or systems. One Technology Way, P.O. Box 9106, Norwood, MA , U.S.A. Tel: Fax: Analog Devices, Inc. All rights reserved.

2 TABLE OF CONTENTS Features... 1 Applications... 1 General Description... 1 Basic Operation... 1 Revision History... 2 EVAL-INAMP-62RZ Details... 3 Quick Start for the EVAL-INAMP-62RZ Board... 4 Circuit Options... 4 Load Resistor... 4 Guard Drivers...5 User Options...6 Quick Start for the EVAL-INAMP-82RZ and EVAL-INAMP- 82RMZ Boards...7 Reference...7 Input...7 Output...7 Ordering Guide...8 ESD Caution...8 REVISION HISTORY 11/08 Rev. 0 to Rev. A Combined AD623-EVALZ and AD623-EVAL Data Sheets... Universal Added AD8220/AD8221-EVALZ Throughout... 1 Changed AD623-EVALZ to AD620 Series-EVALZ Throughout... 1 Changes to General Description... 1 Added EVAL-INAMP-62RZ Details Heading... 3 Added Quick Start for the EVAL-INAMP-62RZ Boards Heading... 4 Changes to Adjustment Section... 4 Added Table 1 and Table 2; Renumbered Sequentially... 4 Changed Appendix Heading to User Options... 6 Added Quick Start for the EVAL-INAMP-82RZ and EVAL-INAMP-82RMZ Boards Heading... 7 Changes to Ordering Guide /07 Revision 0: AD623-EVALZ Initial Version 6/03 Revision 0: AD623-EVAL Initial Version Rev. A Page 2 of 8

3 EVAL-INAMP-62RZ DETAILS GND2 IN REMOVE W3 AND W4 FOR AC COUPLING. R2 100Ω W3 GUARD GUARD GND1 GND W2 C6 C12 10µF 25V C11 10µF 25V 8 1 A2 AD708J 7 C A2 6 4 AD708J V AUX R4 100Ω W7 W6 C1, V AUX W8 W9 0 W5 W4 5 C3, R5 2 R6 2 R3 100kΩ 1 R G R5 100kΩ 1 C4 A R G 6 1 R G REF NOTES 1 INSTALL FOR AC COUPLING ONLY. 2 TO USE GUARD DRIVER, INSTALL R5 AND R6 INSTEAD OF R G. R5 AND R6 = 0.5R G. V AUX V AUX C C9 Figure 1. EVAL-INAMP-62RZ (AD620 Series) Schematic Diagram COMPONENTS IN SHADED AREAS ARE USER SUPPLIED. R8 C10 OFFSET ADJ A1 2 4 EXT_REF V AUX R1 100kΩ V AUX OP177 CS2 J µA R9 5.9kΩ, 1% R10 5.9kΩ, 1% C7 V C8 AUX CS2 J500 OP µA Rev. A Page 3 of 8

4 QUICK START FOR THE EVAL-INAMP-62RZ BOARD CIRCUIT OPTIONS Single-Supply Operation A jumper is provided to select between single or dual power supplies. The evaluation board is shipped with 4 in the dualsupply position. To convert to single supply, place 4 in the position marked with a ground symbol. Adjustment The gain of the AD621 is pin selectable where G = 1 (default) or G = 100 (strap Pin 1 and Pin 8). In contrast, the gain of the AD620, AD622, and AD623 devices is resistor dependent (the resistor is connected between the RG pins). Without a resistor, the gain is unity. Table 1 to Table 3 provide calculated gains for each device. See the individual product data sheet for the gain equations. Table 1. AD620 Resistor Values 1% Standard Value of RG (Ω) Calculated 0.1% Standard Value of RG (Ω) Calculated 49.9 k k k k k k k k k k Table 2. AD622 Resistor Values Desired 1% Standard Value of RG (Ω) Calculated k k k k k k k Table 3. AD623 Resistor Values Desired 1% Standard Value of RG (Ω) Calculated k k k k k k k k k External Reference or Offset Adjustment When shipped, the reference of the EVAL-INAMP-62RZ board is connected to ground. Certain single-supply applications (for example, an ADC connected to the output of the in-amp) require a symmetrical output voltage centered on a nonzero value. The reference can be equal to half the supply, or an application-specific voltage can be provided by an ADC. The user can install a jumper at 3 and connect an external reference to the EXT_REF pin. To maintain proper operation of the in-amp, the reference should be provided by a voltage source. Similarly, a provision is made for an offset adjustment of ±1.12 V by installing the parts listed in Table 6. Although the A2 and A3 ICs can be used with a single or dual power supply connection, A1 requires a dual supply. To enable the offset feature, install a shunt in Position 1. To adjust the offset of the in-amp, ground both inputs and measure the output voltage. Adjust Potentiometer R1 for 0 V. LOAD RESISTOR Although not required for normal operation, a load resistor can be inserted at Position R8. Rev. A Page 4 of 8

5 GUARD DRIVERS When interference from sources such as power lines must be reduced to levels below those provided by standard shielded cables, guard drivers may be effective. A guard equalizes the ac potential between the in-amp input and the cable shield of the line, effectively reducing the low frequency interference voltage. A2 in Figure 2 is a dual op amp AD708 driving the shield(s) of the input cable(s) from the gain resistor pins of the in-amp. The voltages at these pins are equal to the input voltages plus 0.6 V (refer to the device data sheet). The EVAL-INAMP-62RZ provides single and differential guards. Differential guards drive the shields with essentially the same signals as the inputs, whereas the single guard can be used for dual conductor cables. In this mode, the GUARD drives the shield at ½(VIN DIFF) 0.6 V. To activate the guard drivers, VAUX and VAUX must be connected. For shielded cables at both inputs, install the, W2, W5, and W8 jumpers. Using a Single Guard When using the AD620, AD622, and AD623 for gains greater than 1, install Resistors R6 and R11 (which are each half the calculated resistance of RG) and Jumpers, W2, and 0. For a gain of 1, either Position R6 or Position R11 can be shorted to enable the guard driver input. Connect the shield to GUARD. On the header pins that do not bear the ground symbol, insert a shunt across Position. The guard drivers can be assembled using the components listed in Table 6. POWER INPUT Figure 2. Component Location for the EVAL-INAMP Rev. A Page 5 of 8

6 USER OPTIONS Table 4. Jumpers Jumper Function Description Status GUARD select Allows the shield of the positive input cable to be connected to the guard driver or ground. Not installed W2 GUARD select Allows the shield of the negative input cable to be connected to the guard driver or ground. Not installed W3 Input coupling Installed; the positive input is dc-coupled. Installed W4 Input coupling Installed; the negative input is dc-coupled. Installed W5 Guard driver IN Connects the negative shield guard driver to Pin 1 of the in-amp. Not installed W6 VS to VAUX Connects the negative supply voltage to the negative auxiliary voltage of the same value. Not installed W7 VS to VAUX Connects the positive supply voltage to the positive auxiliary voltage of the same value. Not installed W8 Guard driver IN Connects the positive shield guard driver to Pin 8 of the in-amp. Not installed W9 Guard driver IN Connects the positive shield guard driver to ground. Not installed 0 Guard driver IN Selects the single-shield guard driver. Not installed 1 Reference input Connects the reference of the in-amp to the offset-adjustable voltage reference. Not installed 2 Reference input Connects the reference of the in-amp to ground. Installed 3 Reference input Connects the reference of the in-amp to an external reference supply. Not installed 4 In-amp VS source Connects the in-amp VS pin to GND or to VS of the evaluation board. Connected to VS 5 Guard driver IN Connects the negative shield guard driver to ground. Not installed Table 5. Input/Output I/O VS/ VS GND IN/ IN GUARD/ GUARD EXT_REF VAUX/ VAUX Function Positive and negative rails of the in-amp. Ground for the board. GND1, GND2, GND3, and GND4 designate pins. Positive and negative inputs of the in-amp. Positive and negative terminals for use with a shielded cable. External reference input for the in-amp. Output of the in-amp. Auxiliary power rails for guard drivers and offset reference circuitry. Table 6. User-Supplied Parts for Guard and Offset Circuits Reference Designation Part Guard Drivers C5, C6 0.1 μf, 25 V ceramic capacitor A2 AD708JN dual precision op amp Offset Regulators C7 to C μf, 25 V ceramic capacitor A1 OP177 precision op amp CS1, CS2 J μa current source R9, R kω, 1% metal film resistor Rev. A Page 6 of 8

7 QUICK START FOR THE EVAL-INAMP-82RZ AND EVAL-INAMP-82RMZ BOARDS The quick start instructions in this section assume that the evaluation board is in default condition as shown in Table 7. Separate evaluation boards are available for the AD822x SOIC for MSOP devices (see the Ordering Guide section.) Table 7. Factory Setting Connection is soldered Purpose REF is tied to ground Follow Step 1 through Step 3 to get started using these boards (see Figure 3). 1. Connect a ±2.3 V to ±15 V supply to VS and VS. 2. Drive the inputs with a signal. 3. Measure the output on a multimeter or oscilloscope. The output voltage is the voltage measured between VOUT (OUT) and VREF (REF). The output can drive another device, such as an ADC. IN R1 IN 4 R G 3 R G µF REFERENCE 10µF 8 7V OUT OUT DUT 6V REF 5 REF Figure 3. EVAL-INAMP-82RZ Schematic SMA/SMB CONNECTOR (OPTIONAL) The reference level of the instrumentation amplifier can be set by driving the REF pin with a precision voltage reference or by using the solder jumper,. By default, is soldered, shunting REF to ground. If a reference voltage other than ground is used, the solder must be removed from before driving REF with the reference voltage as shown in Figure 4. IN 1V p-p, 1kHz 5V 10µF 10V DUT 0V 10µF OUT REF 5V OSCILLOSCOPE Figure 4. Using an External Voltage Source to Set the Reference Level (Circled) COM INPUT The in-amp inputs should not be left floating, that is, without a DC return path. This often occurs when the inputs are connected to a transformer, a thermocouple, or a pair of series capacitors. The inputs should have a dc path to ground, as shown in Figure 4 and Figure 5. The circuit shown in Figure 5 has series capacitors, C1 and C2, between the signal generator and the input. The series capacitors prevent a dc current from flowing into the input transistors of the instrumentation amplifier. Two matched 10 kω resistors are used between the instrumentation amplifier inputs and ground to provide the necessary current path. These resistors should be closely matched to reduce offset and CMRR errors. C1 C2 IN 10kΩ R1 499Ω 10kΩ 10µF 15V 10µF DUT 15V OUT REF OSCILLOSCOPE Figure 5. AC Input Coupling, Using a Resistive DC Return Path COM Output measurements should be made by monitoring the voltage between the OUT and REF tie points of the board as shown in Figure 6. If an external voltage reference is used, the output can be measured, referred to ground, as shown in Figure 4. The evaluation board offers an SMA/SMB outline. By default, the output voltage measured using an SMA/SMB connector is with respect to ground. 500mV p-p, 100Hz 10V p-p, 10Hz IN R1 5.49kΩ 10µF 15V 10µF DUT 15V OUT REF Figure 6. Correct Output Connection Using the REF Pin OSCILLOSCOPE COM Rev. A Page 7 of 8

8 ORDERING GUIDE Model EVAL-INAMP-62RZ 1 EVAL-INAMP-82RZ 1 EVAL-INAMP-82RMZ 1 1 Z = RoHS Compliant Part. Description AD620 Series SOIC Evaluation Board AD8220 Series SOIC Evaluation Board AD8220 Series MSOP Evaluation Board ESD CAUTION Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. EB /08(A) Rev. A Page 8 of 8